Cementitious panels have been used in the construction industry to form the interior and exterior walls of residential and/or commercial structures. The advantages of such panels include resistance to moisture compared to standard gypsum-based wallboard. However, a drawback of such conventional panels is that they do not have sufficient structural strength to the extent that such panels may be comparable to, if not stronger than, structural plywood or oriented strand board (OSB).
Typically, the cementitious panel includes at least one hardened cement composite layer between layers of a reinforcing or stabilizing material. In some instances, the reinforcing or stabilizing material is fiberglass mesh or the equivalent. The mesh is usually applied from a roll in sheet fashion upon or between layers of settable slurry. Examples of production techniques used in conventional cementitious panels are provided in U.S. Pat. Nos. 4,420,295; 4,504,335 and 6,176,920, the contents of which are incorporated by reference herein. Further, other gypsum-cement compositions are disclosed generally in U.S. Pat. Nos. 5,685,903; 5,858,083 and 5,958,131.
U.S. Pat. No. 6,620,487 to Tonyan, which is incorporated herein by reference in its entirety, discloses a reinforced, lightweight, dimensionally stable panel capable of resisting shear loads when fastened to framing equal to or exceeding shear loads provided by plywood or oriented strand board panels. The panels employ a core of a continuous phase resulting from the curing of an aqueous mixture of calcium sulfate alpha hemihydrate, hydraulic cement, an active pozzolan and lime, the continuous phase being reinforced with alkali-resistant glass fibers and containing ceramic microspheres, or a blend of ceramic and polymer microspheres, or being formed from an aqueous mixture having a weight ratio of water-to-reactive powder of 0.6/1 to 0.7/1 or a combination thereof. At least one outer surface of the panels may include a cured continuous phase reinforced with glass fibers and containing sufficient polymer spheres to improve nailability or made with a water-to-reactive powders ratio to provide an effect similar to polymer spheres, or a combination thereof.
US Patent Application Publication No. 2005/0064055 to Porter, application Ser. No. 10/665,541, which is incorporated herein by reference in its entirety, discloses an embedment device for use in a structural panel production line wherein a slurry is transported on a moving carrier relative to a support frame, and chopped fibers are deposited upon the slurry, includes a first elongate shaft secured to the support frame and having a first plurality of axially spaced disks, a second elongate shaft secured to the support frame and having a second plurality of axially spaced disks, the first shaft being disposed relative to the second shaft so that the disks intermesh with each other. The intermeshing relationship enhances embedment of the fibers into the slurry and also prevents clogging of the device by prematurely set slurry particles.
US Patent Application Publication No. 2005/0064164 to Dubey et al., application Ser. No. 10/666,294, incorporated herein by reference in its entirety, discloses a multi-layer process for producing structural cementitious panel which includes: (a.) providing a moving web; (b.) one of (I) depositing a first layer of individual, loose fibers upon the web, followed by depositing a layer of settable slurry upon the web and (ii) depositing a layer of settable slurry upon the web; (c.) depositing a second layer of individual, loose fibers upon the slurry; (d.) actively embedding said second layer of individual, loose fibers into the slurry to distribute said fibers throughout the slurry; and (e.) repeating steps (ii) through (d.) until the desired number of layers of settable fiber-enhanced slurry is obtained and so that the fibers are distributed throughout the panel. Also provided are a structural panel produced by the process, an apparatus suitable for producing structural cementitious panels according to the process, and a structural cementitious panel having multiple layers, each layer created by depositing a layer of settable slurry upon a moving web, depositing fibers upon the slurry and embedding the fibers into the slurry such that each layer is integrally formed with the adjacent layers.
U.S. Pat. No. 6,986,812 of Dubey et al., incorporated herein by reference in its entirety, features a slurry feed apparatus for use in a SCP panel production line or the like application where settable slurries are used in the production of building panels or board. The apparatus includes a main metering roll and a companion roll placed in close, generally parallel relationship to each other to form a nip in which a supply of slurry is retained. Both rolls preferably rotate in the same direction so that slurry is drawn from the nip over the metering roll to be deposited upon a moving web of the SCP panel production line. A thickness control roll is provided in close operational proximity to the main metering roll for maintaining a desired thickness of the slurry.
U.S. Patent Application Publication No. 2006/0174572 to Tonyan et al., incorporated herein by reference in its entirety, discloses non-combustible SCP panel metal frame systems for shear walls.
U.S. Pat. No. 6,248,214 to Stotz et al. disclose a pivot headbox for a paper machine. See column 7, lines 14-46 referring to FIG. 2, axis 24a provided in the area of the nozzle end or stream outlet 15 so that a corresponding nozzle stream angle change. The Stotz headbox, which is more similar to an extrusion device than an open headbox, uses a cylinder underneath the headbox (item 12) to control the angle of tilt and is very limited in adjustment of the angle of tilt compared to the degree of adjustment with a simple lever on the pivot shaft of the headbox used in the present invention.
U.S. Pat. No. 4,479,987 to Koepke et al. discloses a free-falling liquid curtain 4 which is laterally guided by two sheets of material through a very restricted area defined by curtain holders 9 which are vertically arranged (col. 6, lines 58-59). The arrangement would not be operable with a cement slurry which contains lumps and chips and which is fast setting. This arrangement would cause plugging of the area between the curtains, resulting in a broken curtain of slurry deposited on the web. The ability of the vertical curtains to pivot without the curtain tearing is largely through use of an auxiliary liquid delivered through a supply pipe, 10. This which would be impractical with an aggressive setting cement slurry which is used in the present invention.
U.S. Pat. No. 4,420,371 to Dahl et al. discloses a pivoting paper headbox apparatus which uses a captive shaft through a typical bearing or other means of pivot that is actuated by a jack or cylinder at the rear of the machine, compared to the single hand operated lever attached to the pivot shaft in the present invention. The pivot shaft in the present invention is set into a yoke which only allows up and down movement for easy removal of the device from the line but does not permit the device to move in the direction of the conveyor belt. The headbox in Dahl is also designed to isolate the headbox from vibration from adjacent equipment, rather than being designed to vibrate the headbox to maintain the flow and distribution of the slurry in the headbox of the present invention.
U.S. Pat. No. 4,165,211 to Ebeling et al. discloses an apparatus for applying a layer of liquid foamable reaction mixture to a continuously moving support. According to one particular embodiment, the distributor channel is adapted to pivot about an axis extending transversely to the conveyor belt (col. 2, lines 53-58). This pivoting action enables the volume in the distributor channel and hence the time of intermediate storage of the reaction mixture in the channel to be controlled (See FIG. 1, and column 3, lines 31-47). The Ebeling device would allow heavy cement particles to eventually settle out, filling the bottom radius of the headbox right up to the discharge lip. The present invention uses a combination of vibration and headbox angle control the discharge flow pattern of the headbox. The angle of tilt is used to ensure material is consistently discharged from the headbox to ensure a curtain is maintained. The pivot on the present headbox is placed so as to minimize the change in distance between spillway lip and the product being formed compared to the Ebeling device in which the pivot is placed in the approximate center of the headbox. The pivoting action of the Ebeling device appears to be limited to controlling flow of the device and would not allow for immediate dumping of headbox contents on the belt as in the present invention.
U.S. Pat. No. 3,360,392 to Mod et al. discloses a reservoir 38 and spout 39 (FIG. 2 and column 2, lines 63-70). The headbox in Mod does not provide for pivoting of the headbox or for vibration of the headbox to maintain the flow and distribution of a slurry in the headbox to provide depositing of a continuous curtain of slurry on the web, as in the present invention.
In preparing the SCP panels, an important step is feeding cementitious slurry to the production line. There is a desire for improved slurry feeing devices to increase production speed and reduce downtime.
There is also a desire for an improved process and/or a related apparatus for producing fiber-reinforced cementitious panels which results in a board with structural properties comparable to structural plywood and OSB which reduces production line downtime. There is also a desire for a process and/or a related apparatus for producing such structural cementitious panels which more efficiently uses component materials to reduce production costs over conventional production processes.
Furthermore, the above-described cementitious structural panels, also referred to as SCP's, are preferably configured to behave in the construction environment similar to plywood and OSB. Thus, the SCP panels are preferably nailable and can be cut or worked using conventional saws and other conventional carpentry tools. Further, the SCP panels should meet building code standards for shear resistance, load capacity, water-induced expansion and resistance to combustion, as measured by recognized tests, such as ASTM E72, ASTM 661, ASTM C 1185 and ASTM E136 or equivalent, as applied to structural plywood sheets.
The improvements noted in co-pending U.S. Patent Application Publication No. 2008/0099171 A1, allowed for a headbox that would provide a robust and continuous slurry. However, certain problems and deficiencies associated with this technology include numerous electrical controls (2 motors and 2 limit switches), a large footprint of about 3 linear feet on the line, which obscures physical and visual access to the forming area (which can allow flaws to go undetected for longer periods of time), slurry leakage at the ends of the rolls and between the roils (due to wear and inability to provide for robust sealing methods), inadequate stirring and movement of the slurry within the headbox with use of the rotating rolls to move slurry in the headbox, difficult cleaning due to materials used and complexity of the headbox which leads to high fabrication cost.